This invention relates to restoration of disrupted traffic in a telecommunications network and more particularly the use and coordination of a plurality of restoration processes in the telecommunications network.
To ensure that traffic disrupted by a failure in any span or link of a telecommunications network, such as for example by a cut of the link or a span, a restoration process whereby an alternate path is found for rerouting the disrupted traffic is needed. In fact, a combination of various restoration processes may be used under different circumstances for different purposes. There are at least three such different restoration processes that could operate after a disruption has occurred in the network for finding an alternate path to circumvent the disruption.
The first process is a simple one to one automatic line protect switching (ALPS) scheme in which a dedicated link is provided between adjacent nodes for reestablishing the path between the adjacent nodes were the link that ordinarily carry traffic between the adjacent nodes malfunctioned. Thus, when the working link connecting the adjacent nodes is cut, the disrupted traffic is quickly routed to the dedicated back-up link between the adjacent nodes.
A second approach for restoring traffic in a telecommunications network is a distributed restoration algorithm (DRA) scheme in which the spare links among the neighboring spans of adjacent nodes are used for finding an alternate route for rerouting the traffic disrupted between the adjacent nodes. This restoration process is more adaptative and sophisticated than the ALPS scheme. However, it also requires more intelligence and a somewhat longer operational time.
A third process involves the use of a central network operation center, which takes control following a failure anywhere within the network, so as to coordinate either a preplanned scheme or an ad hoc switching scheme for restoring the disrupted traffic. The time frame for such centralized operation ranges from seconds to hours, particularly if human intervention is needed.
Although the use of a combination of the three just mentioned restoration processes, and other restoration processes not mentioned herein, is desirable in a telecommunications network, a problem does arise in that the switching actions performed by one process may undermind the desired operation of another. In other words, the different restoration processes cannot operate simultaneously or smoothly with one another.
A need therefore exists for assuring that the various restoration processes be properly coordinated if those processes were to work in conjunction with each other in a telecommunications network.
To accomplish the proper coordination among the different layers of restoration processes in a telecommunications network provisioned with such restoration processes, the present invention method first determines the portions of the telecommunications network that are provisioned with the different restoration processes. This is needed insofar as only a certain portion of a network may in actuality be provisioned for distributed restoration. Once that is determined, if a disruption does occur, assuming that the DRA restoration process would first take place at the DRA provisioned portion of the network, the instant invention would request the operation support system (OSS) that oversees the DRA provisioned nodes, or digital cross-connect switches (DXCs) or intelligent devices, to order the DRA provisioned nodes to cease any DRA operations after the DRA process has been terminated. This is done by the DRA OSS broadcasting a disabled DRA message to those nodes that are DRA provisioned. In receipt of such a disabled DRA message, each of the DRA provisioned nodes then determines whether or not it is actively effecting a DRA operation in response to a failure. If it is not, the node would enter into a DRA disabled mode and respond to the DRA OSS with a disable acknowledge message. On the other hand, if the node is indeed actively engaged in a DRA restoration process, a DRA in progress message is returned to the DRA OSS. Thereafter, such node continues its DRA process until it reaches a safe stopping point. At which time the node enters into the DRA disabled mode and issues a disable acknowledge message to the DRA OSS.
When the DRA OSS has received from each of the relevant DRA provisioned nodes a disable acknowledge message, it forwards to the non-DRA OSS an indication that the non-DRA process can begin.
When the non-DRA restoration process is finished, the DRA OSS is requested to re-enable those DRA provisioned nodes to reactivate their DRA processing. An enable DRA message is then broadcast to all of the relevant DRA provisioned nodes.
The present invention technique therefore involves the controller of a first given restoration process requesting the controller of a second restoration process to cease operation and to give the first given restoration process control only when all of the nodes effecting the second restoration process have provided an acknowledgment that cessation has taken place. This request and acknowledge process is repeated for the various layers of restoration processes, so that coordination of the different restoration processes can be effected.
An objective of the present invention is therefore to provide a method for coordinating the respective operations of different restoration processes of a telecommunications network.
It is another objective of the present invention to provide a telecommunications network provisioned with a DRA scheme and other non-DRA schemes a method of mediating the operation of those various schemes.